This invention relates to methods of automatically aligning IC-chips (integrated circuit chips) with a target in a system where the target has a set of co-ordinates which are indeterminate. This invention also relates to apparatus for automatically performing such methods.
In the prior art, one particular method of the above type is described in U.S. Pat. No. 6,774,651. This patent '651 issued on Aug. 10, 2004, and is entitled METHOD FOR ALIGNING AND CONNECTING SEMICONDUCTOR COMPONENTS TO SUBSTRATES.
FIG. 4 of patent '651 illustrates one preferred apparatus which performs the patented method. This apparatus includes a platform assembly 22 which is moveable, and a chuck assembly 24 which is stationary and spaced-apart from the platform assembly 22.
The platform assembly 22 includes a vacuum nozzle 38 which holds an IC-chip 10. The vacuum nozzle 38 is attached to, and moved by, a hexapod which is comprised of six linear actuators 34. This hexapod is able to move the IC-chip 10 parallel to three orthogonal axis, and is able to rotate the IC-chip 10 about those three axis.
The chuck assembly 24 holds a substrate 12 for the IC-chip 10. Thus, the substrate 12 is the target with which the IC-chip 10 needs to be aligned. More specifically, the IC-chip 10 has a face 13 with one set of electrical contacts 14; the substrate 12 has a face 15 with another set of electrical contacts 16; and these two sets of electrical contacts need to be aligned with each other and connected together.
To perform the alignment process in patent '651, the platform assembly 22 includes one height gauge 42 and one camera 44; and, the chuck assembly 24 also includes one height gauge 52 and one camera 50. How these four components are used in the alignment process is described in patent '651 at line 37 of column 7 to line 11 of column 8, which is quoted below.
“During an aligning and connecting process, the moving platform 32 can be moved such that the height gauge 42 is proximate to the substrate 12, and is able to determine the distance between the height gauge 42 and the substrate 12. This distance information can be converted into a signal, which can be optically or electrically transmitted to the controller 46. The distance information gives a Z-axis coordinate for the substrate 12.”
“Similarly, the moving platform 32 can be moved such that the camera 44 is proximate to the substrate 12 and can generate an image of the facing surface 15 of the substrate 12. The visual image can be used to identify three reference points X1, X2, X3 (FIG. 3) on the facing surface 15. The references points X1, X2, X3 can be known features of the substrate 12, such as the substrate contacts 16, or can be dedicated alignment fiducials formed on the substrate 12. This image is then converted into a signal which can be optically or electrically transmitted to the controller 46. By noting the X-axis and Y-axis coordinates of the reference points X1, X2, X3, and the Z-axis coordinate obtained by the height gauge 42, the position and orientation of the plane containing the reference points can be determined. This calculation can be performed by the controller 46 or can be performed by another computer (not shown) in signal communication with the controller 46.”
“The position and orientation of the component 10 can be determined in a similar manner. Specifically, a camera 50 and a height gauge 52 are mounted on a base 48 of the chuck assembly 24. Operation of the platform assembly 22 allows the component 10 to be placed proximate to the height gauge 52 to determine distance information and the Z-axis coordinate of the component 10. Similarly, the component 10 can be placed proximate to the camera 50, and a visual image can then be obtained and communicated to the controller 46. The visual image can be used to identify the X-axis and Y-axis coordinates of at least three points Y1, Y2, Y3 (FIG. 3) on the facing surface 13 of the component 10. Again the three points can be features such as the component contacts 14 or can be dedicated alignment fiducials. Using this information and the Z-axis coordinate from the height gauge 52, the orientation and position of the component 10 can be calculated by the controller 46 or another computer in signal communication with the controller.”
From the above quote, it is clear that the alignment method of patent '651 depends on obtaining two dimensional images from the cameras 44 and 50, and digitally processing those images. In particular, reference points X1, X2, and X3 need to be identified in the two dimensional image of surface 15 on the substrate 12, and reference points Y1, Y2, and Y3 need to be identified in the two dimensional image of surface 13 on the IC-chip 10. Then, the X and Y co-ordinates of these reference points in the actual three dimensional system need to be determined from the two dimensional images. By comparison, with the present invention, no cameras are used and no digital images are processed.
Several alternative embodiments to the FIG. 4 apparatus are also shown in FIGS. 5-10 of patent '651. However, each of those alternative embodiments still include the two cameras that were described above.
Also in the prior art, another method of automatically aligning IC-chips with a target is described in U.S. Pat. No. 6,587,743. This patent '743 issued on Jul. 1, 2003, and is entitled PICK AND PLACE TEACHING METHOD AND APPARATUS FOR EMPLEMENTING THE SAME.
FIG. 1A of patent '743 illustrates a side view of one particular system which implements the claimed method. This FIG. 1A system includes a vacuum nozzle 15 which moves parallel to three orthogonal axis X, Y, and Z, and which also rotates around the Z axis.
As one step of the alignment process, the laser source 50 emits a laser beam in the X-Y plane, while the vacuum nozzle 15 is moved along the Z-axis through the laser beam. This step is described in patent '743 at lines 1-8 of column 7, which is quoted below.
“The Z-axis initialization is described in FIG. 2. In preferred aspects, the laser align system is used to determined the Z=0 point. Z=0 is defined as that point at which the laser align unit transitions between being able to “see” nozzle 15 and being unable to see nozzle 15. That is, the position is defined such that nozzle 15 blocks the laser align beam for all positive Z and does not block the beam for all negative Z.”
As another step of the alignment process, the laser source 50 emits a laser beam in the X-Y plane, while the vacuum nozzle 15 holds an electronic device (such as an IC-chip) which is rotated around the Z-axis in the laser beam. This step is described in patent '743 at lines 38-50 of column 9, which is quoted below.
“Briefly, the laser align unit takes measurements as the device is rotated. For example, one or more sensors monitor which of one or more laser beams is interrupted during a rotation of the device. At any given time the image can be characterized by a width and a center position. The laser align unit identifies the four positions (corresponding to the four sides of the device) at which the image exhibits local width minima, and returns the center position associated with each of the four positions. Using these four center coordinates, the software is able to compute a correcting move for the X, Y, and angle coordinates.”
From the above two quotes, it is seen that the alignment method in patent '743 depends on the emission of a laser beam by a source that is spaced-apart from a laser sensor, and the detection of when the emitted beam is broken by an object which is moved in a straight line or rotated between the source and the sensor. By comparison, with the present invention, no such breakage of a laser beam occurs.